A method of manufacturing rimless spectacles is known in which connecting elements of the lugs and the bridge of the spectacles are adhesively bonded to the front sides of the lenses. In this known method firstly two lens blanks are fabricated of a plastic material to the front and rear sides of which a coating is applied. The two coated lens blanks are ground such that two spectacle lenses having a desired lens shape are obtained. At predetermined mounting positions for the connecting elements of the lugs and the bridge on the front side of the lenses the coating is removed to form joining surfaces substantially corresponding, as to shape and dimensions, to joining surfaces formed at the connecting elements. The connecting elements are then adhesively bonded to the front side of the lenses at the mounting positions. Since in the area of the joining surfaces at the spectacle lenses the base material thereof is exposed, a permanently tight adhesive bond can be produced between the connecting elements and the lenses.
Furthermore, an apparatus adapted to be employed in the afore-described method for forming the joining surfaces on the front sides of the lenses by local abrasion of the coating in the area of the joining surfaces is also known. This apparatus includes a mounting plate as well as a holding device for each lens of the spectacles to be manufactured with the aid of which the lens is fixed to the mounting plate such that its front side faces away from the mounting plate and is exposed. A grinding device comprises a drive unit and a tool supported by the drive unit in the form of a face grinder. Being controlled by a program control means the grinding device can be moved above the location at which an individual joining surface is to be formed, is lowered there until the end face of the face grinder contacts the lens with low pressing force and then locally abrades the coating in order to form a joining surface at the lens. It has turned out to be difficult to form the joining surfaces exactly at the positions predetermined for the same on the front side of the lens by means of the known apparatus.